PhoneSat is a technology demonstration mission, a picosatellite of NASA/ARC (Ames Research Center) based on a 1U CubeSat form factor. The objective of the project is to use a commercial mobile telephone (smartphone) as an avionics system in a nanosatellite. The overall goals are to: 1)2)3)

• Increase on-orbit processor capability by a factor of 10-100

• Decrease the cost by a factor of 10-1000

• Free up the CubeSat volume for additional payload through avionics miniaturization

The objective of the two PhoneSat-1.0 units is to demonstrate the use of Nexus S smartphone, the flight avionics for a small satellite (1U CubeSat). The two PhoneSat 1.0 CubeSats are battery-powered (lithium-ion battery). They are required to stay alive in space for only a short period and send back health and picture data. Communications is provided by a radio beacon and a watchdog circuit. The latter provides simple monitoring of the systems and reboots the phone if radio packets stop being sent.

The PhoneSats will also use their off-the-shelf built-in cameras to take pictures of the Earth from orbit.

PhoneSat-2.0

A beta version of PhoneSat 2.0 joins the two battery-powered PhoneSat 1.0 spacecraft. PhoneSat 2.0 is built around an updated Nexus S smartphone made by Samsung Electronics which runs Google's Android operating system to provide a faster core processor, avionics and gyroscopes. The objective of the one 1U PhoneSat-2.0 unit is to demonstrate the smartphone as the flight avionics, a low cost reaction wheel-based attitude control system, and solar cell power (to enable a longer duration mission).

For launch, the CubeSats will be integrated into an ISIPOD CubeSat deployer built by ISIS (Innovative Solutions in Space) of Delft, The Netherlands. Once the pod is released from Antares, it will deploy the cubesats individually. The small craft will drift in low Earth orbit for about two weeks before re-entering the atmosphere. If the cubesats can survive several orbits and keep in contact with controllers on the ground, the demonstration will be considered a success.

All 3 spacecraft have corner reflectors to assess the laser communications potential for CubeSats. The mass of each CubeSat is ~ 1.2 kg.

The PhoneSat-2.0 configuration provides new features:

• Solar panels

• Reaction wheels

• Magnetorquers

• 2 way radio (µHard 2420 system)

• Nexus-S.

RF communications: The PhoneSat satellites are emitting packets over the amateur radio band at 437.425 MHz. All three satellites transmit using AFSK (1200 bit/s) modulation, AX.25 packet coding and have vertical linear polarization. 4)

Figure 2: ADCS functional block diagram (image credit: AMES)

Launch: Three NASA PhoneSat systems (two PhoneSat 1.0's CubeSats and one PhoneSat 2.0 CubeSat) were launched on April 21, 2013 on the maiden flight of the Antares-110 vehicle of OSC (Antares is the renamed Taurus-2 launch vehicle of OSC for medium-class payloads). The launch site was the Wallops Flight Facility, Wallops Island, VA. 5)6)7)8)

The primary payload on this test flight is a Cygnus capsule mass simulator of ~3800 kg (of Orbital Sciences/NASA), a heavily instrumented payload to gather data on the launch environment aboard Antares. The launch is funded under the NASA COTS (Commercial Orbital Transportation Services) program. 9)

Ten minutes after liftoff, the rocket released its payload, a simulated Cygnus spacecraft and several smallsats, into low Earth orbit, ending a successful mission.

The launch was a major success for both Orbital and NASA. For Orbital, Antares represented not only the largest rocket the company had ever built, but also a major bet on the company’s future. Orbital hopes Antares can launch not just Cygnus cargo missions, but other satellites, for the US government in particular, that previously flew on the Delta II, a medium-class rocket that will be retired in the next few years. Antares will provide “right-size and right-price” launch services, as the company terms it, for such payloads, a subtle reference to the fact that such satellites now have to use the larger, and more expensive, EELV-class Atlas V and Delta IV. - For NASA, the launch was another vindication of its approach to turn to the commercial sector to launch cargo and, eventually, crews to the ISS. 10)

The Antares picture perfect liftoff marked the first step in a PPP (Public/Private Patnership) between NASA and Orbital Sciences to restart cargo delivery services to the ISS that were lost following the forced retirement of NASA’s space shuttle orbiters.

The four small satellites were deployed from two ISIPODs (ISIS Payload Orbital Dispensers) that were integrated with the mass simulator. 12)

Figure 4: Photo of the Cygnus mass simulator capsule after its separation from the Antares rocket (image credit: OSC) 13)

Legend to Figure 4: The image was taken by a camera onboard the upper stage of the Antares rocket. Both the mass simulator and upper stage of the Antares vehicle are expected to stay in orbit for several months before their orbits degrade and they reenter and burn up in the atmosphere before reaching Earth's surface.

Vision: The current vision beyond PhoneSat 2.0 is twofold: (1) to start using the PhoneSat 2.0 bus to do science and exploration missions — i.e. start utilizing the benefits of PhoneSat and (2) to continue to push forward breakthrough technologies that enable (a) an increase in capabilities and (b) a decrease in cost.

There are several directions that each could take: dispersed sensor heliophysics missions, missions to do space qualification of components, debris or NEO (Near Earth Orbit) tracking, low cost Earth observation, Lunar and other exploration missions, add GPS, foldable design. These can all lead to significant new performance. The GPS receiver could enable an array of missions not possible without. The foldable design would entail compacting the PhoneSat bus into a smaller volume which folds out. This would enable multiple satellites to be launched per 1U size and since launch costs dominate, a lower overall mission cost. The PhoneSat 2 year milestone is to have iterated through several designs to produce a PhoneSat 3.0 which supports the vision beyond PhoneSat 2.0 with a primary focus on (a) dispersed sensors mission support and (b) a foldable design. The vision is to continue to “decrease” the cost AND “increase” the capability. Pursue both vectors simultaneously. 14)

PhoneSat mission status:

• May 2, 2013: For about one week, engineers at NASA/ARC, Moffett Field, Calif., and amateur radio operators around the world collaborated to reconstruct an image of Earth sent to them from three smartphones in orbit. The joint effort was part of NASA's nanosatellite mission, called PhoneSat, which launched on Sunday, April 21, 2013 aboard the Antares rocket from NASA's Wallops Island Flight Facility in Virginia. 15)

Although the ultimate goal of the PhoneSat mission was to determine whether a consumer-grade smartphone can be used as the main flight avionics for a satellite in space, the three miniature satellites used their smartphone cameras to take pictures of Earth and transmitted these "image-data packets" to multiple ground stations. Every packet held a small piece of "the big picture." As the data became available, the PhoneSat Team and multiple amateur ham radio operators, who call themselves "hams," pieced together a high-resolution photograph from the tiny data packets.

Piecing together the photo was a very successful collaboration between NASA's PhoneSat team and volunteer amateur ham radio operators around the world. NASA researchers and hams working together was an excellent example of Citizen Science, or crowd-sourced science, which is scientific research conducted, in whole or in part, by amateur or nonprofessional scientists. On the second day of the mission, the Ames team had received over 200 packets from amateur radio operators.

Figure 5 is such a reconstructed image from packets received by amateur radio operators (image credit: NASA).

• The orbital analysis of the PhoneSat team indicates that the PhoneSats have deorbited on April 27, 2013 and have burned up in Earth's atmosphere as predicted. No one has been able to hear from the satellites since, which confirms the predictions. The mission is considered a success. - The PhoneSat team will continue to develop the PhoneSats using consumer technology to greatly increase the capability of the satellite whilst developing with a low cost. 16)17)

- Over the course of five days in space the trio of PhoneSats operated as planned, according to NASA. The spacecraft could prove to be the lowest-cost satellites ever flown in space, NASA researchers say. 18)

Figure 5: Photo of Earth transmitted from PhoneSat "Alexander" (PhoneSat-1.0) and reconstructed from packets received by amateur radio operators (image credit: NASA)

• April 22, 2013: Transmissions from all three PhoneSats have been received at multiple ground stations on Earth, indicating they are operating normally. The PhoneSat team at the Ames Research Center in Moffett Field, CA, will continue to monitor the satellites in the coming days. The satellites are expected to remain in orbit for as long as two weeks. 19)20)

The information compiled and edited in this article was provided byHerbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.